Biomass conversion: Sugar hydrogenolysis, glycerol dehydroxylation and HF saccharification

In the current research, three biomass conversion processes, namely sugar hydrogenolysis, glycerol dehydroxylation and HF saccharification, are investigated. The sugar hydrogenolysis process converts sugars into glycerol, propylene glycol and ethylene glycol; the glycerol dehydroxylation process converts glycerol to 1,3-propanediol; while the HF saccharification process converts lignocellulosic biomass into sugars.; The current research on sugar hydrogenolysis has focused on understanding of the reaction mechanism and of the factors controlling the reaction selectivity. In the mechanism study, a series of 1,3-diol model compounds have been hydrogenolyzed, to establish the mechanism of C-C and C-O bond cleavage in sugar hydrogenolysis. The experimental work confirmed our theoretical conception that the C-C bond breaks via the retro-aldol reaction of a beta-hydroxyl carbonyl precusor, and it also provided for the first time direct evidence that the C-O cleavage is through dehydration of the same beta-hydroxyl carbonyl precursor just mentioned. Establishment of the above mechanism makes it possible for one to adopt a more rational approach than the current practice in control of the selectivity of sugar hydrogenolysis.; The selectivity study in the current work has focused on control of the C-O cleavage in sugar hydrogenolysis. Specifically, an experimental study, as well as a simulation study, has been carried out in this work to investigate the effect of temperature, base concentration, hydrogen pressure, catalyst amount and catalyst type on the C-C vs C-O selectivity. These studies, both experimental and theoretical, yielded many useful results.; In the research on conversion of glycerol to 1,3-propanediol, a new concept is proposed to selectively transform the second hydroxyl group of glycerol into a tosyloxy group, and then to remove it by hydrogenolysis. The technical feasibility of this new concept is verified experimentally in this work. Before this work, hydrogenolysis of tosylates, are generally effected with base metal hydrides, such as LiAlH4 and LiHBEt3. In this work, for the first time, tosylates with a hydroxy group adjacent to the tosyloxy group are hydrogenolyzed with molecular hydrogen in the presence of a nickel or ruthenium catalyst. The mechanism for this hydrogenolysis reaction is also established.; The work on vapor-phase HF saccharification has focused on modeling of the HF adsorption process in a packed-bed reactor. However, experiments were also conducted with a bench-scale reactor to study the behavior of HF adsorption in the packed-bed reactor. Two models of HF adsorption have been developed. One is developed purely based on experimental observations, and the other one is developed based on a detailed analysis of the HF flow, the intrinsic HF adsorption and the heat transfer processes occurring in the reactor during HF adsorption. These models provide a great deal of insight into the HF adsorption process in the packed-bed reactor.